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Arctic Circle
The Arctic Circle is one of the five major that mark maps of the Earth. For Epoch 2011, it is the parallel of that runs north of the Equator.[http://bbs.keyhole.com/ubb/ubbthreads.php?ubb=showflat&Number=1157795&site_id=1#import Trópico en movimiento (in Spanish)] The region north of this circle is known as the , and the zone just to the south is called the . The equivalent in the is called the Antarctic Circle. The Arctic Circle marks the southern extremity of the polar day (24-hour sunlit day, often referred to as the "midnight sun") and polar night (24-hour sunless night). North of the Arctic Circle, the sun is above the for 24 continuous hours at least once per year and below the horizon for 24 continuous hours at least once per year. On the Arctic Circle those events occur, in principle, exactly once per year, at the June and December solstices, respectively. In fact, because of and because the sun appears as a disk and not a point, part of the midnight sun may be seen on the night of the northern summer solstice up to about 50 (90 km) south of the Arctic Circle; similarly, on the day of the northern winter solstice, part of the sun may be seen up to about 50 north of the Arctic Circle. That is true at sea level; those limits increase with elevation above sea level although in mountainous regions, there is often no direct view of the true horizon. The position of the Arctic Circle is not fixed, but directly depends on the Earth's , which fluctuates within a margin of 2° over a 40,000 year period,Arctic Circle notably due to s resulting from the . The Arctic Circle is currently drifting northwards at a speed of about 15 m per year, see for more information. __TOC__ Geography Relatively few people live north of the Arctic Circle due to the . The three largest communities above the Arctic Circle are situated in Russia: (population 325,100), (135,000), and (85,000). (in Norway) has about 68,000 inhabitants. In contrast, the largest North American community north of the circle, (Greenland), has approximately 5,000 inhabitants, while between Canada and the USA, is the largest settlement with circa 4,000 inhabitants. (in Finland), which lies slightly south of the line, has a population of approximately 58,000, and is the largest settlement in the immediate vicinity of the Arctic Circle. The Arctic Circle passes through the , the , , and . The land on the Arctic Circle is divided among eight countries: , , , , the ( ), , ( ), and (where it passes through the small offshore island of ). Starting at the Prime Meridian and heading eastwards, the Arctic Circle passes through: | |} See also *Antarctic Circle * * * *Tropic of Cancer *Tropic of Capricorn * * References External links *Terra Incognita: Exploration of the Canadian Arctic—Historical essay about early expeditions to the Canadian Arctic, illustrated with maps, photographs and drawings * Temporal Epoch Calculations ©2006 by James Q. Jacobs Download: Epoch v2009.xls (modify D4) * Useful constants" See: Obliquity of the ecliptic * ArcticFocus Facts and news about Arctic Category:Geographical features of the Earth